Recovery and purification of materials by electrodialysis



n 1933. R. A. GORTNER ET AL ,5

RECOVERY AND PURIFICATION OF MATERIALS BY ELECTRODIALYSIS Filed Aug. 20, 1928 Int/6W5- Eoss \flz'ken Gariner ,wal'ier Ffloffmaw Pafent Je -27, 1 933 STA ROSES .2. .1

9 m orricr.

amine, or sit. PAUL, AND WALTER r. norrnun, or cnoeum, m'mm- BO'BA, ASSEGNORS .10 FOREST Perm COHEANY, 0F CLOQUET, MINNEQOTA, A

OOQRATIQN 6F HINKESQTA.

' RECQY AND rumroarroir OF MATERIALS BY ELEO'IBODIALYSIB Application filed August 20, 1928. Serial No. 300,663.

The present invention relates to the treat ment of certain products or compounds containing both mineral and organic matter in association, such as the metal salts of organic acids, to break down the compounds or to separate mineral from organic portions.

it has particular reference to the treatment of natural products, such as fruits and vegetable matter containing useful substances of pectin-like character.

lhe invention relatesnot only to the isolation of such materials but also to the purification of similar products otherwise isolated or prepared. 7

Natural pectin is believed to be a metal salt of an organic acid which acid has characteristic properties making it readily recoverable by the process of the present invention after the metal has been removed from the salt. Pectin occurs in nature in many fruits and vegetables as a calcium or magnesium salt of an acid. It is found in vegetables such as carrots and turnips, in leaves, in apples and many other iruits, es pecially the lemon and grapefruit of the citrus family. All of these materials may housed as raw material for the present invention when pectin is desired. It is preferred to use the pulp and rinds ofthe citrus fruits, and the vegetable tubers. Pulp of ap les is readily obtainable as a raw material, known as apple pomace, and 1t 1s at present one very important commercial source of pectin produced by chemical extraction. Pectin is employed largely in food products, such as jelly, and it is a particular substance determining the elation of natu ral fruit juices. ln puri ed and concentrated form it is available on the market for addition to foods tocause gelation.

in use, pectin functions not as a salt but as the free acid, and it is prepared for the market as the free acid. As such it is lruorvn as pectin. It is colloidal in nature in wter, and for that reason it is readily prepar by the present invention.

In order to illustrate the invention the process ofpreparing pectin will be described in detail. The inventionis therefore not to be sc considered as limited to application for the broader in scope and applicable to other processes. as expressed in the a pended claims.

The usual method 0 preparing pectin comprises extraction from its source with an appropriate solvent, precipitating the pectin from the solvent, and further purifying the precipitated product. The process requires a number of steps, special attention, and a variety of reagents; audit is a iii: cult and expensive process compared to the process of the present invention. This can be ascertained by reference to Bare in the J ournal of Industrial and Engineering Chemistry, vol. 16, page 1042 (192d) Generally, the present invention as applied to pectin comprises subjecting the source of pectin to the disruptive edect of an electric potential and the resulting current so that the metal portion is freed from the organic nucleus, and carrying the freed metal away from the source and the resulting organic residue by the migratory influence of the current. v

. The process may be carried out in apparatus having the essential features or the exemp'lary cell shown in the accompanying drawing. A box-like structure 10 has three compartments of which 11 is the product compartment in which the raw material is.

placed and the product obtained. Raw materialis indicated by the numeral 12. The

cell has other compartments, herein shown current is attended by the migration of charged particles towards the electrodes. Positively charged particles move toward the cathode l5 and negatively charged particles move toward the anode 16. charged particles which may be present. in-

The

efliciency o the clude ions, such as cations and anions of may be colloids. Some ions may be present which are colloidal in size and which do not pass through asuitably chosen membrane.

maller ions may readily pass the membrane, but non-ionic and colloidal particles and the ions of colloidal ma itude are restrained by the membrane. embranes of collodion cellophane, animal tissue, and materials of similar closed structure are suitable for the urpose, and in the drawing are indicated y the numerals 17 and 18, each membrane bein supported on both sides by sheet materia such as canvas 19.

Means is provided to keep the particular ionic concentrations in the electrode chambers at a lower value than the concentration of similar ions in the productchamber. This is best accomplished by dilution of the liquid in the-electrode chambers. Where water is employed as a conducting and ionizing medium an inflow of water is provided at 20 and an outflow at 21.

In operation to roduce pectin, the middle compartment may packed with an aqueous suspension of lemon pulp or pulped'rinds, or other pectin-bearing substance, such as apple pomace. The consistency of the mixture o pul and water has a bearing on the rocess. If a low pulp concentration is used current is carried largely by the water;,and in-s ite of the fact that a proportionately smal er amount of material is introduced to be recovered from the pulp, it will take a much longer time than .if greater amounts of pulp are employed for the same volumeof the mixture, and a much greater power consumption per unit of prod- I uct will result. If too much pullp and too In lacin the pulp into the compartment a little water are used, the pulp w ack and form a mechanical barrier to the mi ration of the ions, and the. colloid particles ormed will also contribute to establish the barrier.

'su cient ooseness should be malntained to provide liquid channels through the compartment wherein the ions may. migrate freel The natural vegetable material is an examp e of solid material havin a-high specific surface, due to the fibrous c aracter of the vegetable matter. There are indications that there is aconducting path along the sur-" face ofthe fiber which has less resistance than a similar water channel, and this is believed to be due to 'the' formation of electwo adjacent paths of high conductivity.

that when pulp is present in suflicient quans v aths across the-prodWticom jartment, the e ectrical and tity to establish such surface time eficienc o the'process is greatly im proved and t recess made commerciall practicable. erence is made to the applicants joint Patent N 0. 1,878,235 of September 20, 1932, for further explanation of the increased efliciency hereinabove described.

- Any potential may be applied across the electrodes, but-preferably one is chosen so that an eflective current flows in quantity insufficient to cause undue heating of the mass. A current density of about one-half to two amperes per square foot of compartment cross section is maintained. It is to be understood that as the treatment progresses,

.the electrolytes are removed from the middle compartment into the electrode compartments and from there washed out of the apparatus. In consequence the internal resistance of the cell will increase, and a change in applied otential may be desirable to maintain .an efective current. The current is continued until the desired quantity of the metal component ofthe natural pectin has been removed leaving the e uivalent in free acid pectin. This acid is col oidal and-but sli htly ionized. The colloidal free acid, the resi ual pulp and any other solids which may be presentare restrained bythe membranes from leaving the product compartment. Any free acids'which accompany t e pectin in the source, or which may be formed in the process, and which are ionized, such as citric acid, are moved as anions into the anode compartment in amount depending in part upon the ionic concentration. When the desired degree of completion or purification of the process has been attained the current is stopped and the colloidal solution of the ctin is mechanically separated from the solid parts in the middle compartment. The pulp ma be discarded and the pectin product in co loidal solution may be concentrated to form a syrup, or otherwise recovered.

It is readily seen that an impure tin may be treated in the same way for t e removal of mineral matter or of contaminating electrolytes, such as citric acid, or other ionizing compounds, so as to concentrate in the product the desired pectin substance.

This is preferably done in the presence of 7 free acid, such as citric, may be present, and

this may aid in causing the separation of the .metal and the organic radicle' so that the metal component may be carried away by the electric current.

The invention therefore contemplates the presence or the addition 9f electrolytes -which may aid in the separationand removal of the components of the base material. Although we have shown water as the vehicle for migration it is well known that other liquid media are electrically conductive 'andcan induce ionization of com ounds.

therefore, contemp tes any suitable elec- The invention,

nausea unetal ions when joined toacids as in the a formation of salts. It will be readily understood that the present invention is applicable to materials of pectin-like character which may be associated with pectin, and which may be related thereto, and which may function like pectin. The invention contemplates not only the preparation and purification of pectin nthe manner herein described, but also the purification of pectin concentrates however they may be obtained. Reference is made to applicants copending application 29 Serial No. 621,868, filed July 11, 1932, wherein the product is described and claimed. The present application relates to the process as defined by the appended claims.

We claim;

l. e method of extracting pectin-like substance from containing material which com rises suspending the material in water a p ying an electric potential to create an e ective current through the mass, permit 39 ting ions to move away from the material, restraining movement of the material and the resulting pectin-like substance, and separating the resulting solution oi the pectin-like product from sa d material.

, $5 2. The method of securing pectous substance which comprises suspending material containing pectin in water, ap lying an electric potential to create an e ective current through the mass, permitting ions to more fill away from the mass, restraining movement of the material and the resulting pectin prodnot, and separating the solution of the pectin from said material.

3. The method ofsecuring'pectous subl- 4%. The method of securing ectous substance which comprises suspen ing pectin- 5 containing material in water in an electric cell, passingan electric current through the cell, permitting the resulting ions to migrate towards the electrodes, restraining the movement of the material and the pectin product,

m removing impurities collected at the electrodes, and recovering ectin from the material remainin in the ce l.

5. The met od of securinga soluble ctous substance which com rise's-suspen ing at pectin-containing materia in Whig in an electric .cell, passing an electric current through the cell, permitting the resulting ions to migrate towards'the electrodes, restraining movement of the material and the residual soluble pectous product,-and separating the soluble pectous productrfrom the material remaining in the cell.

6. The method of securing pectous substance which comprises suspendlng material containing pectin in water in an electric cell, passing an electric current through the cell, permitting the resulting ions to migrate towards the electrodes, restraining movement of the material and the pectin product,

.maintaining at the electrodes" a concentration of impurities from the mass which lower than the concentration remaining in the mass, and recovering pectin from the material remaining in the cell.

7. The method of purifying a pectous sub-. stance from associated metal capable of forming cations, which comprises mixing the material to be purified with an electrically conducting and ionizing medium, a'p lying an electric potential to create an e 'ective current through the mass, permitting the cations to migrate out of the mass, and restraining movement of the resulting pectous product from the mass.

8. The method of treating a pectin product Ill associated with metal capable of forming ca- Y tions which comprises placing the pectin product in water in a chamber of an electric cell provided with? pectin restraining diaelectricity between the diaphragms, whereby cations are removed from the mass, and removin the resulting pectin solution from the pn p.

9. The method of treating a pectin product associated with metal capable of forming cations which comprises placing the pectin product in water in a chamber of an electric cell having pectin restraining diaphra ms in the presence or a solid material or high s ecific surface packed between the dia- 'p ms with the provision of liquid channels across the chamber between the diaphra w subjecting the material in the chem er to a flow ofdirect current of electricity between the diaphregms, whereby cations are removed from the mass, and removing the resulting pectin solution from the solid material. 10. The method of producingpectin from citrus fruits which consists of packing a pulp derived-from citrus fruits containing pectin into an electricdia hragm cell, submerging the packed materia with water, assing a 'direct current of electricity throng the cell,

ermitting cations to leave the mass, restrainill? lid

Elm

i,91 5,668 ing movement of the resulting tin fro n the mass, and removing the resu ting pectin solution from the pulp.

In witness whereof we have hereunto afixed our signatures.

ROSS AIKEN GORTNER. WALTER F. HOFFMAN.- 

